1,2-diaminocyclohexane platinum (ii) complexes having antineoplastic activity

ABSTRACT

Organoplatinum complexes having antineoplastic activity against the L1210 mouse leukemia test system and having sufficient water-solubility for use in aqueous i.v. fluids. The organoplatinum complexes include malonato (1,2-diaminocyclohexane) platinum (II), hydroxymalonato (1,2-diaminocyclohexane) platinum (II), dinitrato (1,2-diaminocyclohexane) platinum (II), sulfato (1,2-diaminocyclohexane) platinum (II), and hydroxonitrato (1,2-diaminocyclohexane) platinum (II).

BACKGROULD OF THE INVENTION

This invention relates to organoplatinum complexes and, moreparticularly, to 1,2-diaminocyclohexane platinum (II) complexes havingantineoplastic activity against the L1210 mouse leukemia test system.

In the last several years, a number of organoplatinum complexes havebeen synthesized and reported as potentially active antitumor agents.One of these compounds, cis-dichlorodiammineplatinum (II), has beenutilized with limited success in cancer chemotherapy of man, but due toits toxic side effects, has a rather low therapeutic index.

Subsequent efforts to find other organoplatinum complexes having highertherapeutic index values led to the synthesis and testing of dichloro(1,2-diaminocyclohexane) platinum (II) and also malonato(1,2-diaminocyclohexane) platinum (II). Connors et al (Chem.-Biol.Interactions, Volume 5, pages 415-424, 1972) assessed antitumor activityof dichloro (1,2-diaminocyclohexane) platinum (II) against the ADJ/PC6Aplasma cell tumor in mice, and reported LD₅₀, ID₅₀, and therapeuticindex values quite similar to those of cis-dichlorodiammine-platinum(II). Cleare et al (Bioinorganic Chemistry, Volume2, pages 187-210,1973) investigated the antitumor activity against the Sarcoma 180 inSwiss mice, of both dichloro (1,2-diaminocyclohexane) platinum (II) andmalonato (1,2-diaminocyclohexane) platinum (II), and found both of thesecomplexes to have only marginal antitumor activity and to be much lessactive than cis-dichlorodiammineplatinum (II). Neither Connors et al norCleare et al presented any data on the effects of these complexes on themore highly predictive L1210 leukemia in mice, nor did they use thesecomplexes in combination chemotherapy with other antineoplastic agents.

In an extension of the work reported by Connors et al and Cleare et al,the present inventors and co-workers (Gale et al, ResearchCommunications in Chemical Pathology and Pharmacology, Volume 7, No. 3,pages 529-538, March 1974) demonstrated that dichloro(1,2-diaminocyclohexane) platinum (II) was highly effective againstL1210 leukemia in mice, providing an increase of up to 54 percent inmean survival time in comparison with cis-dichlorodiammineplatinum (II),and furthermore that it could be combined synergistically with the knownantineoplastic agent cycloposphamide. These results were veryencouraging since effectiveness against the L1210 leukemia in mice isgenerally considered as being a highly predictive indication of apotentially clinically useful antineoplastic agent. However, one seriousdrawback to the potential clinical utility of dichloro(1,2-diaminocyclohexane) platinum (II) is the fact that this complex isvery insoluble in aqueous i.v. fluids, necessitating its administrationintraperitoneally as a slurry in water. Since intravenous, rather thanintraperitoneal, administration is generally required for clinicaleffectiveness, a clinically useful antineoplastic agent should havesufficient water-solubility for use in aqueous i.v. fluids.

SUMMARY OF THE INVENTION

It is accordingly a primary object of the present invention to provideorganoplatinum complexes having increased water-solubility.

Another object of this invention is to provide organoplatinum complexesin accordance with the preceding object, which are soluble in aqueousi.v. fluids used for intravenous administration.

A further object of the invention is to provide organoplatinum complexesin accordance with the preceding objects, which exhibit antineoplasticactivity against the highly predictive L1210 mouse leukemia in mice.

Still another object of the invention is to provide organoplatinumcomplexes in accordance with the preceding objects, which exhibit ahigher level of antineoplastic activity against the L1210 mouse leukemiatest system in comparison with the prior art derivatives previouslyproposed for this purpose.

The above and other objects are achieved in accordance with the presentinvention by providing novel 1,2-diaminocyclohexane platinum (II)complexes having the formula ##STR1## wherein X is a monodentate anionicligand selected from the group consisting of - ONO₂ and ##STR2## ortogether with Y a bidentate anionic ligand of the formula ##STR3## whenX is-ONO₂, Y is-ONO₂ or-OH; and when X is ##STR4## Y is-OH₂.sup.(+). Theorganoplatinum complexes coming within Formula I as defined aboveinclude hydroxymalonato (1,2-diaminocyclohexane) platinum (II),dinitrato (1,2-diaminocyclohexane) platinum (II), sulfato(1,2-diaminocyclohexane) platinum (II), and hydroxonitrato(1,2-diaminocyclohexane) platinum (II). The present invention alsoinvolves the known organoplatinum complex, malonato(1,2-diaminocyclohexane) platinum (II), which has the same formula asFormula I above, but with X and Y together being a bidentate anionicligand of the Formula ##STR5##

The above-described organoplatinum complexes have been found to haveincreased water-solubility in comparison with the prior art dichloro(1,2-diaminocyclohexane) platinum (II) complex and to be soluble inaqueous i.v. fluids used for intravenous administration. Specifically,these organoplatinum complexes have been found to be effective for thetreatment of the highly predictive L1210 leukemia in mice, and in thisregard, moreover, to exhibit a higher level of antineoplastic activityin comparison with the prior art dichloro (1,2-diaminocyclohexane)platinum (II) complex.

DESCRIPTION OF PREFERRED EMBODIMENTS

The 1,2-diaminocyclohexane platinum (II) complexes in accordance withthe present invention are as follows: ##STR6## malonato(1,2-diaminocyclohexane) platinum (II) ##STR7## hydroxymalonato(1,2-diaminocyclohexane) platinum (II) ##STR8## dinitrato(1,2-diaminocyclohexane) platinum (II) ##STR9## sulfato(1,2-diaminocyclohexane) platinum (II) ##STR10## hydroxonitrato(1,2-diaminocyclohexane) platinum (II)

The starting material used in the preparation of each of the1,2-diaminocyclohexane platinum (II) complexes in accordance with thepresent invention, is dichloro (1,2-diaminocyclohexane) platinum (II),whose synthesis from potassium tetrachloroplatinite is described idbyGale et al, Research Communications in Chemical Pathology andPharmacology, Volume 7, No. 3, pages 529-538, March 1974. Thepreparation of each of the complexes involves first reactingstoichiometric amounts of the dichloro (1,2-diaminocyclohexane) platinum(II) and the appropriate silver salt in water at room temperature toform a silver chloride precipitate, which is then removed bycentrifugation. The silver salt employed will either be silver nitrateor silver sulphate, depending upon the particular complex being preparedas described be below. The supernatant solution resulting from thecentrifugation is then further treated as described below to yield thefinal complex.

In preparing sulfato (1,2-diaminocyclohexane) platinum (II), silversulphate is used as the silver salt, and the final complex is recoveredfrom the supernatant solution by filtering the solution, drying thefiltrate, washing the residue sequentially with water and methanol, anddrying the washed product.

In preparing dinitrato (1,2-diaminocyclohexane) platinum (II), silvernitrate is used as the silver salt, and the final complex is recoveredfrom the supernatant solution by filtering the solution, drying thefiltrate, taking up the residue in water and filtering, washing theproduct on the filter paper sequentially with dilute nitrate acid andwater, and drying the washed product.

Hydroxonitrato (1,2-diaminocyclohexane) platinum (II) is prepared byusing silver nitrate as the silver salt, and then adding ammoniumhydroxide to the supernatant solution. The solution is then evaporated,the residue washed sequentially in water, alcohol and ether, and thewashed product then dried.

In preparing malonato (1,2-diaminocyclohexane) platinum (II), silvernitrate is used as the silver salt, and the supernatant solution afterbeing filtered is further reacted with malonic acid. The reactionmixture is then filtered, and the retained precipitate washed with waterand then dried. Hydroxymalonato (1,2-diaminocyclohexane) platinum (II)is prepared in the same manner, but substituting hydroxymalonic acid forthe malonic acid.

All five of the 1,2-diaminocyclohexane platinum (II) complexes inaccordance with the present invention have increased water solubility incomparison with dichloro 1,2-diaminocyclohexane) platinum (II). Forexample, whereas the dichloro derivative has a water solubility of lessthan 0.1mg/ml, the water solubilities, in mg/ml, of the malonato complexis 0.3; the hydroxymalonato complex, 1.5; the nitrato complex, 3.0; thesulfato complex, greater than 15.0; and the hydroxonitrato complex,30.0. All five of the complexes in accordance with the present inventionhave sufficient water-solubility for use in aqueous i.v. fluids used forintravenous administration.

In addition to having increased water-solubility in comparison withdichloro (1,2-diaminocyclohexane) platinum (II), the1,2-diaminocyclohexane platinum (II) complexes in accordance with thepresent invention have also been found to exhibit significantly higherlevels of antineoplastic activity against the L1210 leukemia in mice,which is generally regarded as being a highly predictive in vivo testsystem for indicating the potential clinical usefulness of a drug as anantineoplastic agent for the treatment of animal tumors. Thesignificance of this test system in evaluating potential antineoplasticagents and the test protocol therefor, are described in detail by Geranet al, "Protocols for Screening Chemical Agents and Natural ProductsAgainst Animal Tumors and Other Biological Systems" (Third Edition),Cancer Chemotherapy Reports, Part 3, Volume 3, No. 2, Pages 1-103,September 1972. Briefly, the test procedure involves implanting L1210leukemia cells into mice by intraperitoneal (i.p.) injection, beginningi.p. treatment with the test drug 24 hours after implant, anddetermining the antineoplastic activity of the test drug at optimum doselevels and schedules of administration as the percent increase in lifespan (%ILS) of the treated mice over the untreated control mice.

The % ILS values obtained with the 1,2-diaminocyclohexane platinum (II)complexes in accordance with the present invention against the L1210leukemia test system indicate that these complexes have considerablygreater potency as antineoplastic agents against this test system thanthe prior art dichloro (1,2-diaminocyclohexane) platinum (II), bothindividually and when used in combination chemotherapy with otherantineoplastic agents. The increased potency against the L1210 leukemiatest system exhibited by the malonato complex of Formula II, above, incomparison with the dichloro complex, is particularly noteworthy in viewof the previous reports described above that such malonato complex hasonly marginal antitumor activity against the Sarcoma 180 in mice.Moreover, the novel hydroxymalonato complex of Formula III, above, hasbeen found to exhibit an even greater potency against the L1210 leukemiatest system than the known corresponding malonato complex.

Various dose levels of each of the 1,2-diaminocyclohexane platinum (II)complexes of the present invention have been tested against the L1210leukemia in mice, employing three different schedules of administration,designated as schedules A, B and C in Table I, below. Schedule Aconsisted of a single injection administered ip on the first dayfollowing implant of the L1210 leukemia cells.(i.e., 24 hours afterimplant). Schedule B consisted of a three-injection regimen, with oneinjection being administered ip on each of the first, fifth and ninthdays following implant. Schedule C consisted of a nine-injectionregimen, with one injection being administered ip on each of the firstthrough ninth days following implant. The dose ranges for each of thesethree schedules found safe and effective for providing % ILS values ofat least 25% are set forth in Table I, below.

                  TABLE I                                                         ______________________________________                                        1,2-Diamino-                                                                  cyclohexane Plati-                                                                         Dose/Injection, mg/kg                                            num (II) Complex                                                                           Schedule A Schedule B Schedule C                                 ______________________________________                                        Malonato      2.5-160    10-40     5-20                                       Hydroxymalonato                                                                             2-150      5-37.5    1-15                                       Dinitrato     0.5-8      0.25-4    0.05-2                                     Sulfato       0.5-10     0.2-5     0.1-1.2                                    Hydroxonitrato                                                                              2.5-15     1-5       0.3-1.25                                   ______________________________________                                    

The invention is further illustrated by way of the following examples,in which Schedules A, B and C refer, respectively, to the 1-injection,3-injection and 9-injection schedules of administration described above.

EXAMPLE I Dichloro (1,2-Diaminocyclohexane) Platinum (II)

a. Preparation

Dichloro (1,2-diaminocyclohexane) platinum (II) was synthesized asdescribed by Gale et al, Research Communications in Chemical Pathologyand Pharmacology, Volume 7, No. 3, Pages 529-538, March 1974. Thus,Potassium tetrachloroplatinite, K₂ Pt Cl₄ (20mM) in 75ml water was mixedwith 1,2-diaminocyclohexane (20mM) for 3 hours at room temperature. Theinsoluble product was removed by filtration, washed with water and thenwith methanol, and oven-dried. The yield was approximately 90% oftheory. The product was then purified by dissolution indimethylformamide, filtration, and addition of three volumes of methanolor 0.1N HCl. This product was filtered, washed, and dried as above. Theyield in purification was 47%.

b. Antineoplastic Activity

For purposes of comparison with the 1,2-diaminocyclohexane platinum (II)complexes of the present invention, dichloro (1,2-diaminocyclohexane)platinum (II) was tested for its individual antineoplastic activityagainst L1210 leukemia in mice. In this set of tests, the mice received10⁵ L1210 leukemia cells by ip injection, and were divided into groupsof 10, including a control group. The treated groups were treated ipwith the dichloro complex at several different dose levels for each ofthe A, B an C schedules of administration, all mice within the samegroup receiving the same treatment. The highest % ILS values obtainedfor each of the three schedules of administration and the correspondingdose levels are set forth in Table II below.

                  TABLE II                                                        ______________________________________                                        Schedule of  Dose/Injection,                                                  Administration                                                                             mg/kg           % ILS                                            ______________________________________                                        A             6.25           114                                              B            8.0             113                                              C            2.0             153                                              ______________________________________                                    

Also for the purposes of comparison with the 1,2-diaminocyclohexaneplatinum (II) complexes of the present invention, another set of testswas carried out to assess any additive or synergistic effect of thedichloro complex when used in combination chemotherapy with each of thetwo known antineoplastic agents, 1-propanol,3,3'-iminodi-,dimethanesulfonate (ester) hydrochloride (Yoshi-864), andcyclophosphamide. In this set of tests, the mice received by ipinjection 10⁶ L1210 leukemia cells, which produces a somewhat moreadvanced stage of the disease after 24 hours than is obtained upon using10⁵ cells as described in the previous set of tests. The mice were thendivided into groups of 10, including a control group, and all micewithin the same group were given the same treatment. Treatment wasadministered ip employing the A schedule of administration. The dichlorocomplex was employed at a dose of 2.5mg/kg, and the Yoshi-864 andcyclophosphamide were each employed at doses of 75mg/kg. The treatmentstested were each of the three treating agents by themselves and thedichloro complex in combination with each of the other two treatingagents. The resulting % ILS values and the number of mice (out of thegroup of 10) which survived 60 days following implant, are set forth inTable III.

                  TABLE III                                                       ______________________________________                                        Treatment         % ILS    60-Day Survivors                                   ______________________________________                                        Dichloro complex   73      0                                                  Yoshi-864          81      0                                                  Cyclophosphamide   79      0                                                  Dichloro complex & Yoshi-864                                                                    144      0                                                  Dichloro complex &                                                                              467      5                                                  cyclophosphamide                                                              ______________________________________                                    

The results of Table III indicate that in combination chemotherapy thedichloro complex exhibits a synergistic effect with cyclophosphamide,but merely an additive effect with Yoshi-864. Furthermore, since 60-daysurvival is generally regarded as being indicative of a cure, theresults indicate that the dichloro complex has a cure rate of 50% incombination chemotherapy with cyclophosphamide and a cure rate of zeroin combination chemotherapy with Yoshi-864.

EXAMPLE 2 Malonato (1,2-Diaminocyclohexane) Platinum (II)

a. Preparation

To 1.0 gram of dichloro (1,2-diaminocyclohexane) platinum (II) was added0.89 grams of silver nitrate in 20ml of water and the mixture wasstirred at room temperature for at least 3 hours. The suspension wascentrifuged to remove the insoluble silver chloride and then filtered.To the filtrate was added 0.2737 grams of malonic acid which had beenneutralized previously with 2.0 molar potassium hydroxide. This mixturewas stirred at room temperature for 1 hour, filtered, and the retainedprecipitate was washed with water, and then dried. The yield was 63%.

Analysis -- Calculated for C₉ H₁₆ N₂ O₄ Pt: C, 26.28; H, 3.92; N, 6.81;Pt, 47.43. Found: C, 26.04; H, 3.87; N, 6.89; Pt, 47.61.

b. Antineoplastic Activity

The above-prepared malonato complex was tested for its individualantineoplastic activity against L1210 leukemia in mice by the sameprocedure as described for the testing of the dichloro complex inExample I, above. The highest % ILS values obtained for each of the A, Band C schedules of administration and the corresponding dose levels areset forth in Table IV below.

                  TABLE IV                                                        ______________________________________                                        Schedule of  Dose/Injection,                                                  Administration                                                                             mg/kg           % ILS                                            ______________________________________                                        A            40.0            271                                              A             2.5            258                                              B            40.0            157                                              C            10.0            219                                              ______________________________________                                    

As can be seen from a comparison of Table IV and Table II, the % ILSvalues resulting from treatment with the malonato complex wereconsiderably higher than those obtained by treatment under thecorresponding schedule of administration with the dichloro complex, withall three schedules of administration tested. When considering only thehighest % ILS values obtained with each of these two complexes,regardless of schedule of administration or dose level, the level ofantineoplastic activity achieved with the malonato complex was 77%greater than that achieved with the dichloro complex.

The malonato complex was assessed for its additive or synergistic effectin combination chemotherapy with each of the two known antineoplasticagents, Yoshi-864 and cyclophosphamide, employing the test proceduredescribed in Example 1 above for the similar testing of the dichlorocomplex, the only difference being that the malonato complex wasemployed at a dose level of 15mg/kg. The results of this set of testsare set forth in Table V below.

                  TABLE V                                                         ______________________________________                                        Treatment         % ILS    60-Day Survivors                                   ______________________________________                                        Malonato complex   80      0                                                  Yoshi-864         112      0                                                  Cyclophosphamide  118      0                                                  Malonato Complex & Yoshi-864                                                                    149      0                                                  Malonato Complex &                                                            Cyclophosphamide  773      8                                                  ______________________________________                                    

The results of Table V indicate that the malonato complex, like thedichloro complex, exhibits a synergistic effect in combinationchemotherapy with cyclophosphamide, but merely an additive effect incombination chemotherapy with Yoshi-864. A comparison of Table V withTable III shows that in combination chemotherapy with cyclophosphamidethe malonato complex exhibited a considerably higher level ofantineoplastic activity than the dichloro complex, as indicated by a 66%greater % ILS value and a 60% greater cure rate.

EXAMPLE 3 Hydroxymalonato (1,2-Diaminocyclohexane) Platinum (II)

a. Preparation

To 1.0 gram of dichloro (1,2-diaminocyclohexane) platinum (II) was added0.88 grams of silver nitrate, and the mixture was stirred at least threehours in 20.0ml of distilled water. The insoluble precipitate of silverchloride was removed by centrifugation followed by filtration. To theclear filtrate was added 0.3 grams of hydroxymalonic acid; the pH of thehydroxymalonic acid had been adjusted previously to 10 by the additionof 3ml of 2.0 molar potassium hydroxide. This mixture was stirred atroom temperature for 0.5 hours, filtered, and the precipitate was washedwith water. The product was dried in vacuo over fuming sulfuric acid.The yield was 65 percent.

Analysis -- Calculated for C₉ H₁₆ N₂ O₅ Pt: Pt, 45.65. Found: Pt, 45.91.

b. Antineoplastic Activity

The above-prepared hydroxymalonato complex was tested for its individualantineoplastic activity against the L1210 leukemia in mice by the sameprocedure as described for the testing of the dichloro complex inExample I, above. The highest % ILS values obtained for each of the A, Band C schedules of administration and the corresponding dose levels, areset forth in Table VI below.

                  TABLE VI                                                        ______________________________________                                        Schedule of  Dose/Injection,                                                  Administration                                                                             mg/kg           % ILS                                            ______________________________________                                        A            75.0             97                                              B            37.5            162                                              C            15.0            323                                              ______________________________________                                    

As can be seen from a comparison of Table VI and Table II, the % ILSvalues resulting from treatment with the hydroxymalonato complex wereconsiderably higher than those obtained by treatment under thecorresponding schedule of administration with the dichloro complex, withboth the B and C schedules of administration. When considering only thehighest % ILS values obtained with each of these two complexes,regardless of schedule of administration or dose level, the level ofantineoplastic activity achieved with the hydroxymalonato complex was111% greater than that achieved with the dichloro complex. Moreover,using the same criteria in comparing Table VI with Table IV, the levelof antineoplastic activity achieved with the hydroxymalonato complex was19% greater than that achieved with the malonato complex.

The hydroxymalonato complex was also assessed for its additive orsynergistic effect in combination chemotherapy with each of the twoknown antineoplastic agents, Yoshi-864 and cyclophosphamide, employingthe test procedure described in Example I above for the similar testingof the dichloro complex, the only difference being that thehydroxymalonato complex was employed at a dose level of 30mg/kg. Theresults of this set of tests are set forth in Table VII below.

                  TABLE VII                                                       ______________________________________                                        Treatment         % ILS    60-Day Survivors                                   ______________________________________                                        Hydroxymalonato Complex                                                                         118      0                                                  Yoshi-864         117      0                                                  Cyclophosphamide  107      0                                                  Hydroxymalonato complex &                                                     Yoshi-864         342      0                                                  Hydroxymalonato complex &                                                     cyclophosphamide  711      8                                                  ______________________________________                                    

The results of Table VII indicate that the hydroxymalonato complexexhibits a synergistic effect in combination chemotherapy withcyclophosphamide, and also exhibits a synergistic effect, although to asubstantially lesser degree, in combination chemotheraphy withYoshi-864. A comparison of Table VII with Table III shows that incombination chemotherapy with cyclophosphamide, the hydroxymalonatocomplex exhibited a considerably higher level of antineoplastic activitythan the dichloro complex as indicated by a 52% greater % ILS value anda 60% greater cure rate.

EXAMPLE 4 Dinitrato (1,2-Diaminocyclohexane) Platinum (II)

a. Preparation

To 1.0 gram of dichloro (1,2-Diaminocyclohexane) Platinum (II) was added0.88 grams of silver nitrate in 10 to 20 ml of distilled water. Themixture was stirred at least 3 hours at room temperature. The insolublesilver chloride was removed by centrifugation followed by filtration ofthe supernatant solution. The volume of filtrate was reduced by passinga stream of filtered air over it, and the reduced volume was placed in avacuum dessicator to dry completely. The residue was scraped from thebeaker, taken up in a minimal volume of water, filtered, and the producton the filter paper was washed with a small volume of dilute nitric acidfollowed by a small volume of water. The product was finally dried invacuo over fuming sulfuric acid. The yield was 55%.

Analysis -- Calculated for C₆ H₁₄ N₄ O₆ Pt: C, 16.63; H, 3.26; N, 12.93;Pt, 45.02. Found: C, 16.51; H, 3.28; N, 12.88; Pt, 45.10.

b. Antineoplastic Activity

The above-prepared dinitrato complex was tested for its individualantineoplastic activity against the L1210 leukemia in mice by the sameprocedure as described for the testing of the dichloro complex inExample 1, above. The highest % ILS values obtained for each of the A, Band C schedules of administration and the corresponding dose levels, areset forth in Table VIII below.

                  TABLE VIII                                                      ______________________________________                                        Schedule of  Dose/Injection,                                                  Administration                                                                             mg/kg           % ILS                                            ______________________________________                                        A            4.0             113                                              B            4.0             247                                              C            0.5             281                                              ______________________________________                                    

As can be seen from a comparison of Table VIII and Table II, the % ILSvalues resulting from treatment with the dinitrato complex wereconsiderably higher than those obtained by treatment under thecorresponding schedule of administration with the dichloro complex, withboth the B and C schedules of administration. When considering only thehighest % ILS values obtained with each of these two complexes,regardless of schedule of administration or dose level, the level ofantineoplastic activity achieved with the dinitrato complex was 83%greater than that achieved with the dichloro complex.

The dinitrato complex was also assessed for its additive or synergisticeffect in combination chemotherapy with each of the two knownantineoplastic agents, Yoshi-864 and cyclophosphamide, employing thetest procedure described in Example I above for the similar testing ofthe dichloro complex, the only difference being that the dinitratocomplex was employed at a dose level of 3mg/kg. The results of this setof tests are set forth in Table IX below.

                  TABLE IX                                                        ______________________________________                                        Treatment         % ILS    60-Day Survivors                                   ______________________________________                                        Dinitrato complex 110      0                                                  Yoshi-864         116      0                                                  Cyclophosphamide  105      0                                                  Dinitrato complex & Yoshi-864                                                                   529      5                                                  Dinitrato complex &                                                                             703      8                                                  cyclophosphamide                                                              ______________________________________                                    

The results of Table IX indicate that the dinitrato complex exhibits asynergistic effect in combination chemotherapy with cyclophosphamide andalso exhibits a synergistic effect in combination chemotherapy withYoshi-864. A comparison of Table IX with Table III shows that incombination chemotherapy with each of these antineoplastic agents, thedinitrato complex exhibited a considerably higher level ofantineoplastic activity than the dichloro complex. Specifically, incombination chemotherapy with cyclophosphamide, the dinitrato complexexhibited a 51% greater % ILS value and a 60% greater cure rate than thedichloro complex; while in combination chemotherapy with Yoshi-864, thedinitrato complex exhibited a 267% greater % ILS value than the dichlorocomplex and a cure rate of 50% as opposed to 0.

EXAMPLE 5 Sulfato (1,2-Diaminocyclohexane) Platinum (II)

a. Preparation

To 1.0 gram of dichloro (1,2-diaminocyclohexane) platinum (II) was added0.81 gram of silver sulfate in 20ml of distilled water. This mixture wasstirred over night at room temperature. The insoluble silver chloridewas removed by centrifugation followed by filtration of the supernatantsolution. The filtrate was reduced in volume by passing a stream offiltered air over it, and then dried in a vacuum dessicator. The residueafter drying was scraped out onto filter paper in a Buchner funnel andwashed quickly with a small quantity of distilled water followed bywashing with a small quantity of methanol. The product was finally driedin vacuo. The yield was 27%.

Analysis -- Calculated for C₆ H₁₆ N₂ O₅ SPt: Pt, 46.08. Found: Pt,45.73.

b. Antineoplastic Activity

The above-prepared sulfato complex was tested for its individualantineoplastic activity against the L1210 leukemia in mice by the sameprocedure as described for the testing of the dichloro complex inExample I, above. The highest % ILS values obtained for each of the A, Band C schedules of administration and the corresponding dose levels, areset forth in Table X below.

                  TABLE X                                                         ______________________________________                                        Schedule of  Dose/Injection,                                                  Administration                                                                             mg/kg           % ILS                                            ______________________________________                                        A            5.0             116                                              B             3.33           285                                              C            0.6             239                                              ______________________________________                                    

As can be seen from a comparison of Table X and Table II, the % ILSvalues resulting from treatment with the sulfato complex wereconsiderably higher than those obtained by treatment under thecorresponding schedule of administration with the dichloro complex, withboth the B and C schedules of administration. When considering only thehighest % ILS values obtained with each of these two complexes,regardless of schedule of administration or dose level, the level ofanti-neoplastic activity achieved with the sulfato complex was 86%greater than that achieved with the dichloro complex.

The sulfato complex was also assessed for its additive or synergisticeffect in combination chemotherapy with each of the two knownantineoplastic agents, Yoshi-864 and cyclophosphamide, employing thetest procedure described in Example I above for the similar testing ofthe dichloro complex, the only difference being that the sulfato complexwas employed at a dose level of 4mg/kg. The results of this set of testsare set forth in Table XI below.

                  TABLE XI                                                        ______________________________________                                        Treatment         % ILS    60-Day Survivors                                   ______________________________________                                        Sulfato complex   119      0                                                  Yoshi-864          95      0                                                  Cyclophosphamide   97      0                                                  Sulfato complex & Yoshi-864                                                                     528      6                                                  Sulfato complex & -Cyclophosphamide                                                             571      6                                                  ______________________________________                                    

The results of Table XI indicate that the sulfato complex exhibits asynergistic effect in combination chemotherapy with cyclophosphamide,and also exhibits a synergistic effect in combination chemotherapy withYoshi-864. A comparison of Table XI with Table III shows that incombination chemotherapy with each of these antineoplastic agents, thesulfato complex exhibited a considerably higher level of antineoplasticactivity than the dichloro complex. Specifically, in combinationchemotherapy with cyclophosphamide, the sulfato complex exhibited a 22%ILS value and a 20% greater cure rate than the dichloro complex; whilein combination chemotherapy with Yoshi-864, the sulfato complexexhibited a 267% greater % ILS value than the dichloro complex and acure rate of 60% as opposed to 0.

EXAMPLE 6 Hydroxonitrato (1,2-Diaminocyclohexane) Platinum (II)

a. Preparation

To 12.6 grams of dichloro (1,2-diaminocyclohexane) platinum (II) wasadded 1.12 grams of silver nitrate in 20ml of distilled water. Thismixture was stirred over night in a covered flask (to exclude light).The insoluble silver chloride was removed by centrifugation. To theclear supernatant solution 2.0ml of 2 molar ammonium hydroxide was addedto adjust the pH to 4.0. A stream of filtered air was passed over thesolution until it had evaporated almost to dryness. The precipitate wascollected on filter paper in a Buchner funnel and washed, in sequence,with a small quantity of water, alcohol and ether. The resultingmaterial was dried in a vacuum dessicator. The product was very solublein water. The yield was 26%.

Analysis -- Calculated for C₆ H₁₅ N₃ O₄ Pt: C, 18.69; H, 3.89; N, 10.80;Pt, 50.16; O, 16.46. Found: C, 17.75; H, 4.36; N, 11.09; Pt, 49.22; O,17.35.

b. Antineoplastic Activity

The above-prepared hydroxonitrato complex was tested for its individualantineoplastic activity against the L1210 leukemia in mice by a slightlymodified procedure from that described for the similar testing of thedichloro complex in Example I, above. The mice received by ip injection10⁶ L1210 leukemia cells, which produces a somewhat more advance stageof the disease after 24 hours than is obtained upon using 10⁵ cells asdescribed previously. The mice were then divided into groups of six,including a control group. The treated groups were treated ip withvarious dose levels of the hydroxonitrato complex employing the Aschedule of administration, all mice within the same group receiving thesame treatment. The highest % ILS value obtained was 144 at a dose levelof 10mg/kg.

The increased level of antineoplastic activity exhibited by thehydroxonitrato complex in comparison with the dichloro complex becomesreadily apparent when comparing the results of Example 6(b) with TableII above. The results set forth in Table II were obtained under the lesssevere test conditions where the mice being treated had received only10⁵ L1210 leukemia cells. Even so, the highest % ILS value obtained withthe dichloro complex employing the A schedule of administration, wasonly 114. Thus, the 26% greater % ILS value obtained with thehydroxonitrato complex under the more severe test conditions representsa significantly higher level of antineoplastic activity than thatexhibited by the dichloro complex.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. An organoplatinumcomplex having the formula ##STR11## wherein X is a monodentate anionicligand selected from the group consisting of -- ONO₂ and ##STR12## ortogether with Y a bidentate anionic ligand of the formula ##STR13## whenX is -- ONO₂, Y is -- ONO₂ or -- OH; and when X is ##STR14## Y is --OH₂.sup.(+).
 2. The organoplatinum complex of claim 1, consisting ofhydroxymalonato (1,2-diaminocyclohexane) platinum (II).
 3. Theorganoplatinum complex of claim 1, consisting of dinitrato(1,2-diaminocyclohexane) platinum (II).
 4. The organoplatinum complex ofclaim 1, consisting of sulfato (1,2-diaminocyclohexane) platinum (II).5. The organoplatinum complex of claim 1, consisting of hydroxonitrato(1,2-diaminocyclohexane) platinum (II).